In vehicle transmissions, a transmission using a so-called dual-clutch transmission is recently known to eliminate the interruption of transmission of mechanical power when the speed of the mechanical power is changed. The dual-clutch transmission includes two speed change mechanisms, i.e., a first speed change mechanism composed of a first group of speed change stages and a second speed change mechanism composed of a second group of speed change stages that are speed change stages other than the first group of the speed change stages, and further includes a first clutch capable of engaging an input shaft of the first speed change mechanism (hereinafter, described as a first input shaft) with an output shaft of an internal combustion engine (hereinafter, described as an engine output shaft) and a second clutch capable of engaging an input shaft of the second speed change mechanism (hereinafter, described as a second input shaft) with the engine output shaft. Then, dual-clutch transmission shifts gears by alternately engaging the first and second clutches.
Further, in vehicles including an internal combustion engine (engine) and a motor generator (hereinafter, simply described as a “motor”) as prime movers, a vehicle driving apparatus, in which a motor (a rotor of the motor) is coupled with at least one of a first input shaft and a second input shaft of a dual-clutch transmission, is proposed (refer to, for example, Patent Documents 1, 2).
Further, Patent Document 3 described below discloses a mechanical oil pump for generating hydraulic pressure by being operated by the rotation of a rotating shaft (rotor) of a motor coupled with an input shaft of a transmission and supplying the hydraulic pressure to a first clutch and a second clutch. Patent Document 3 discloses to secure hydraulic pressure necessary to an operation for switching an engaged state and a disengaged state of a clutch (hereinafter, described as an “engaging/disengaging operation”) by driving a mechanical oil pump by a motor when an internal combustion engine is not operated (while the engine stops).
Further, Patent Document 4 described below discloses a driving apparatus (a transaxle) in which a motor generator is connected to first and second input shafts of a dual-clutch (double-clutch) transmission and proposes to configure the driving apparatus such that a first engine clutch is ordinarily placed in an engaged state. Patent Document 5 described below discloses a dual-clutch transmission in which a rotor of an electric motor is engaged with one of first and second input shafts. Patent Document 6 described below proposes to configure “a start clutch” disposed between an input shaft of an automatic transmission and an engine such that the start clutch is placed in an engaged state when external power does not act on the start clutch. Patent Document 7 described below proposes to configure a first friction clutch corresponding to a first input shaft of a dual-clutch transmission and a second friction clutch corresponding to a second input shaft of the dual-clutch transmission such that the first friction clutch is placed in a normally disengaged state as well as the second friction clutch is placed in a normally engaged state. Further, Patent Document 8 described below discloses a dual-clutch (twin-clutch) transmission in which a second driving apparatus (drive unit) is connected to a second input shaft.
Patent Document 1: Japanese Patent Application Laid-open No. 2003-79005
Patent Document 2: Japanese Patent Application Laid-open No. 2006-118590
Patent Document 3: Japanese Patent Application Laid-open No. 2007-15679
Patent Document 4: Specification of United States Patent Application Laid-open No. 2002/0088290
Patent Document 5: Specification of United States Patent Application Laid-open No. 2002/0033059
Patent Document 6: Japanese Patent Application Laid-open No. 2003-35360
Patent Document 7: Specification of United States Patent Application Laid-open No. 2006/0230855
Patent Document 8: Specification of United States Patent Application Laid-open No. 2007/0204709